1. Field of the Invention
The present invention relates to members required to have bonding strength, airtightness, and other properties as in the case of bonding a metal to a ceramic. More particularly, the invention relates to a process for producing a ceramic member for bonding and to a ceramic member for bonding, bonded objects, a vacuum switch, and a vacuum vessel.
2. Background Art
The molybdenum-manganese method (Moxe2x80x94Mn method; Telefunken method) has conventionally been known as a method for metallizing a surface of a ceramic base.
In this Moxe2x80x94Mn method, a metallizing ink prepared by adding bonding aids, which help bonding with ceramics, such as a manganese powder, titanium powder, and glass ingredient (SiO2) to a powder of high-melting metals such as tungsten and molybdenum and mixing the powder mixture with an organic binder to make the mixture paste (hereinafter sometimes referred to as xe2x80x9cmetallizing inkxe2x80x9d) is applied to a ceramic base and the ink layer is baked (baking method).
The technique of the related art described above necessitates a baking temperature as high as from 1,300 to 1,500xc2x0 C. for metallization and, hence, has had a problem that the sintering cost regarding furnace structure, utilities, expendable heat-resistant materials, etc. is high.
Another problem is that the ceramic itself deforms in the high-temperature baking, resulting in a product which does not satisfy dimensional accuracy.
Although a measure in overcoming the problem described above may be to bake a metallizing ink having a conventional composition at a temperature lower than 1,300xc2x0 C., this low-temperature baking poses a problem that a sufficient bonding strength cannot be obtained. An improvement in this respect has been desired.
Furthermore, in the case where the metallic layer formed by metallization by the Moxe2x80x94Mn method is to be bonded to another metallic member or the like by brazing, it is necessary to improve the wettability thereof by a brazing material so as to obtain satisfactory bonding. Although it is hence inevitable to conductor post-treatments such as nickel plating and subsequent sintering, there has been a problem that these post-treatments make the protection process complicated.
The invention has been achieved in order to eliminate the problems described above.
an object of the invention is to provide a process by which a ceramic member for bonding having a metallization-deposited metallic film with sufficient bonding strength can be obtained even through low-temperature sintering.
Another object of the invention is to provide a ceramic member for bonding, bonded objects, a vacuum switch, and a vacuum vessel.
In the method of the related art of metallization, metals are bonded to a ceramic mainly by two actions, i.e., the sintering of high-melting metal particles and the diffusion and infiltration of a glass ingredient into spaces among the particles.
When this method of the related art of metallization is conducted at a sufficiently high sintering temperature, not only the sintering of the high-melting metals proceeds to give a metallic layer having improved strength, but also a vitreous ingredient (e.g., SiO2) contained in the ceramic or ink infiltrates into spaces among the high-melting metal particles to mechanically improve the bonding strength based on an anchoring effect. However, in order for the reactions which bring about these effects to proceed sufficiently, a temperature of 1,300xc2x0 C. or higher has been necessary.
In contrast, sintering in the invention can be conducted at a lower temperature because nickel reacts with high-melting metals to accelerate the sintering. In the case where the ink contains SiO2, the metallic layer which is being formed by metallization is sufficiently filled with a vitreous ingredient due to the SiO2, so that baking can be conducted at a temperature as low as, e.g., from 1,080 to 1,250xc2x0 C. (preferably from 1,100 to 1,250xc2x0 C., more preferably from 1,100 to 1,200xc2x0 C.).
The invention has been completed based on that finding. The invention will be explained below.
(1) Those objects are accomplished with the invention of item 1, which is
a process for producing a ceramic member for bonding which comprises mixing a mixture comprising high-melting metal particles of tungsten and/or molybdenum and particles of nickel with an organic binder to produce a paste metallizing ink, applying the metallizing ink to a ceramic base which is a sintered ceramic, and baking the resultant ink layer to form a metallic layer.
In this invention, since the metallizing ink contains nickel, the nickel reacts with high-melting metals to accelerate sintering in the layer which is being formed by metallization, as stated above. Because of this, the metal particles can be sufficiently sintered even at a temperature as low as, e.g., from 1,080 to 1,250xc2x0 C.
As a result, the sintering cost regarding furnace structure, utilities, expendable heat-resistant materials, etc. can be reduced as compared with conventional ones. Moreover, the baking conducted at a low temperature produces a marked effect that the ceramic itself is less apt to deform and high dimensional accuracy is obtained. A further advantage is that since the metal particles can be sufficiently sintered even at such a low temperature, high bonding strength can be secured.
While the organic binder for use in the present invention is not limiting, an organic binder where solid binder (e.g., ethyl cellulose) is dissolved in a solvent (e.g., turpentine oil, butyl glycol) may be used. The organic binder may be used in an amount of about 10 to 35% by weight based on 100% by weight of the total amount of the organic binder and the particle mixture. The solid binder may be used in an amount of about 2 to 4.5% by weight based on 100% by weight of the total amount of the solid binder and the particle mixture.
(2) The invention of item 2 is
the process for producing a ceramic member for bonding, wherein the mixture comprises from 70 to 97% by weight the high-melting metal particles of tungsten and/or molybdenum and from 1 to 10% by weight the particles of nickel.
Since the metallizing ink for use in this invention contains nickel in an amount of from 1 to 10% by weight, the nickel reacts with high-melting metals to accelerate sintering in the layer which is being formed by metallization, as stated above. Because of this, the metal particles can be sufficiently sintered even at a temperature as low as, e.g., from 1,080 to 1,250xc2x0 C. As a result, the same effects as of item 1 are produced.
(3) The invention of item 3 is
the processing for producing a ceramic member for bonding of item 1 or 2, wherein the metallizing ink further contains at least one member selected from the group consisting of from 5 to 10% by weight particles of manganese, from 0.5 to 2% by weight particles of titanium and/or TiH2, and from 2 to 15% by weight particles of SiO2.
In this metallizing ink, the manganese ingredient, serving as a bonding aid, is oxidized by the moisture contained in the sintering atmosphere to thereby improve the wetting ability and flowability of a glass ingredient.
The titanium ingredient, which also serves as a bonding aid, is exceedingly active and hence contributes to chemical bonding to the ceramic base.
Furthermore, SiO2, which is vitreous, infiltrates into spaces among high-melting metal particles to thereby mechanically improve bonding strength based on an anchoring effect. In particular, when sintering is conducted at a low temperature, SiO2 is less apt to be fed from the ceramic member for bonding. Even through such low-temperatures sintering, however, high bonding strength can be obtained by using a metallizing ink to which SiO2 has been added.
(4) The invention of item 4 is
a ceramic member for bonding which comprises a ceramic base which is a sintered ceramic and a metallic layer formed on the ceramic base by metallization, the metallic layer comprising tungsten and/or molybdenum as high-melting metal(s) and particles of nickel.
As explained above with regard to the invention of item 1, since the metallic layer formed by metallization contains nickel, it has undergone sufficient sintering event at a temperature as low as, e.g., from 1,080 to 1,250xc2x0 C. because of the reactions of the nickel with high-melting metals during the sintering for metallization.
As a result, the sintering cost regarding furnace structure, utilities, expendable heat-resistant materials, etc. is low as compared with conventional ones. Moreover, since the ceramic itself is less apt to deform during the baking due to the low baking temperature, this ceramic member for bonding has high dimensional accuracy. Furthermore, even when the sintering is conducted at a low temperature, high bonding strength can be secured.
(5) The invention of item 5 is
the ceramic member for bonding of item 4, wherein the metallic layer contains from 70 to 85% by weight tungsten and/or molybdenum as high-melting metal(s) and from 0.5 to 8.5% by weight nickel.
As explained above with regard to the invention of item 4, since metallic layer formed by metallization contains nickel in an amount of from 1 to 10% by weight, it has undergone sufficient sintering even at a temperature as low as, e.g., from 1,080 to 1,250xc2x0 C. because of the reactions of the nickel with high-melting metals during the sintering for metallization. As a result, the same effects as of item 4 are produced.
(6) The invention of item 6 is
the ceramic member for bonding of item 5, wherein the metallic layer further contains at least one member selected from the group consisting of from 1 to 3% by weight manganese, from 0.05 to 2.5% by weight titanium, and from 8 to 20% by weight SiO2 in terms of silicon oxide amount.
As explained above with regard to the invention of item 3, the manganese ingredient and the titanium ingredient each functions as a bonding aid.
Furthermore, the silicon ingredient functions as vitreous SiO2. This SiO2 infiltrates into spaces among high-melting metal particles to thereby mechanically improve bonding strength based on an anchoring effect. In particular, high bonding strength can be obtained even through low-temperature sintering.
(7) The invention of item 7 is
a bonded object obtained by bonding a metallic member to a ceramic member for bonding of any one of items 4 to 6 through the metallic layer.
The bonded object of this invention is characterized in that a ceramic member of bonding is bonded to a metallic member with the above-described metallic layer comprising ingredients including nickel.
Consequently, this bonded object comprising a ceramic member for bonding and a metallic member bonded thereto can be produced at a reduced cost, and the bonded object obtained has high bonding strength and high dimensional accuracy.
(8) The invention of item 8 is
a bonded object obtained by bonding two ceramic members for bonding of any of items 4 to 6 to each other through the metallic layer of each ceramic member.
The bonded object of this invention is characterized in that two ceramic members for bonding are bonded to each other with the above-described metallic layers comprising ingredients including nickel. The bonding surface of each metallic layer is preferably plated prior to the bonding. A preferred method for the bonding is brazing.
Consequently, this bonded object comprising two ceramic members bonded to each other can be produced at a reduced cost, and the bond object obtained has high bonding strength and high dimensional accuracy.
(9) The invention of item 9 is
a vacuum switch having the bonded object of item 7 or 8.
The vacuum switch of this invention is characterized by having either of the bonded objects described above. An example of this vacuum switch is an electric circuit switch employing a ceramic insulating valve, in particular one suitable for the switching of high-voltage large-current electricity.
(10) The invention of item 10 is
a vacuum vessel comprising the bonded object of item 7 or 8.
The vacuum vessel of this invention (e.g., an insulating valve) is used in e.g., the vacuum switch described above. A vacuum switch (electrical circuit switch) can be fabricated by disposing electrodes and other necessary members in this vacuum vessel.
(11) The invention of item 11, which is
a process for producing a ceramic member for bonding which comprises: a first step in which a first paste prepared by mixing a first mixture comprising molybdenum particles and nickel particles with an organic binder is applied to a ceramic base which is a sintered ceramic and the resultant coating layer is dried to form a first layer; a second step in which a second paste prepared by mixing a second mixture comprising particles of nickel or nickel oxide and at-least one member selected from the group consisting of copper particles, copper oxide particles, manganese particles, and manganese oxide particles or comprising particles of a nickel-copper alloy or particles of a nickel-manganese alloy with an organic binder is applied to the first layer and the resultant coating layer is dried to form a second layer; and a third step in which the first layer and the second layer are heated and baked.
The second mixture for use in this process is a mixture comprising particles of nickel or nickel oxide and at least one member selected from the group consisting of copper particles, cooper oxide particles, manganese particles, and manganese oxide particles or a mixture comprising particles of a nickel-copper alloy or particles of a nickel-manganese alloy.
In this invention, since the first paste contains nickel, the nickel reacts with the molybdenum, which is a high-melting metal, to accelerate sintering in the layer which is being formed by metallization. Because of this, metal particles can sufficiently sinter even at a temperature as low as, e.g., from 1,080 to 1,180xc2x0 C. (preferably from 1,100 to 1,160xc2x0 C.).
As a result, the sintering cost regarding furnace structure, utilities, expendable heat-resistant materials, etc. can be reduced as compared with conventional ones. Moreover, due to the baking conducted at a low temperature, the ceramic itself is less apt to deform and high dimensional accuracy is obtained. Furthermore, since the metal particles can be sufficiently sintered even at such a low temperature, high bonding strength can be secured.
In particular, since the second paste contains copper and/or manganese besides nickel, a lowered melting point can be obtained and a dense alloy layer can be formed (on the layer formed by metallization). Because of this, the ceramic member for bonding can be satisfactorily brazed even without a troublesome post-treatment, e.g., nickel plating, conventionally conducted after baking. Namely, this invention produces a marked effect that a considerable simplification in production process is possible.
Furthermore, since the second layer becomes an alloy, the excessive diffusion of nickel into the first layer, which contains a molybdenum, is diminished. Consequently, the molybdenum can be prevented from excessively sintering to reduce strength.
The baking in the third step is preferably conducted in a moist reducing atmosphere especially at a temperature in the range of from 1,080 to 1,180xc2x0 C., because the product obtained through baking under these conditions has high bonding strength and high airtightness.
The baking in the third step may be carried out at the same time to both of the first and second layers after the second step. The baking of the first layer may be carried out after the first step, and the baking of the second layer may be carried out after the second step.
(2) The invention of item 12 is
the process for producing a ceramic member for bonding of item 11, wherein the first mixture comprises from 70 to 94% by weight the molybdenum ingredient and form 1 to 10% by weight the nickel ingredient.
In this invention, since the first mixture contains at least 1% by weight nickel, the nickel reacts with the molybdenum, which is a high-melting metal, to accelerate sintering in the layer which is being formed by metallization. Because of this, the metal particles can sufficiently sinter even at a low temperature in that range. Moreover, since the nickel content is 10% by weight or lower, the molybdenum can be prevented from excessively sintering and, hence, the strength of bonding between the ceramic base and the layer formed by metallization can be prevented from being insufficient.
Furthermore, since the first mixture contains molybdenum in an amount of from 70 to 94% by weight, a tenacious layer can be formed by metallization.
(13) The invention of item 13 is
the process for producing a ceramic member for bonding of item 11 or 12, wherein the first mixture further contains from 2 to 23% by weight silicon oxide ingredient (e.g., as silicon oxide particles).
In this invention, since the first mixture contains a silicon oxide (SiO2) ingredient in an amount of from 2 to 23% by weight, a higher degree of bonding is attained between the ceramic base and the layer formed by metallization.
(14) The invention of item 14 is
the process for producing a ceramic member for bonding of any one of items 11 to 13, wherein the second mixture comprises from 35 to 75% by weight the nickel ingredient (in particles of nickel or nickel oxide or particles of a nickel-copper alloy or of a nickel-manganese alloy) and from 25 to 65% by weight the copper ingredient (in copper particles, copper oxide particles, or particles of a nickel-copper alloy) or the manganese ingredient (in manganese particles, manganese oxide particles, or particles of a nickel-manganese alloy).
In this invention, since the second mixture contains the nickel ingredient in an amount of from 35 to 75% by weight, the strength of bonding to the layer formed by metallization is high and high airtightness is obtained.
Furthermore, since the content of the copper or manganese ingredient in the second mixture is 25% by weight or higher, the resultant alloy layer has excellent suitability for brazing and high strength. Moreover, since the content of the copper or manganese ingredient therein is 65% by weight or lower, infiltration into the layer which is being formed by metallization can be inhibited and, hence, the strength of bonding between the ceramic base and the layer formed by metallization can be secured.
In the case where the second mixture contains a metal oxide such as nickel oxide or copper oxide, it is preferred to add SiO2 thereto because this addition further improves airtightness.
(15) The invention of item 15 is
a ceramic member for bonding which comprises: a ceramic base which is a sintered ceramic; a metallic layer formed by metallization which is a lower layer deposited on a surface of the ceramic base and comprising molybdenum and nickel; and an alloy layer which is an upper layer comprising nickel and either copper or manganese and deposited on the metallic layer either directly or through an interlayer.
In this invention, since the lower layer formed by metallization contains nickel, it can have undergone sufficient sintering even at a low temperature due to the acceleration of sintering by the nickel during baking.
As a result, the sintering cost regarding furnace structure, utilities, expendable heat-resistant materials, etc. can be low as compared with conventional ones. The low-temperature baking enables the ceramic member to have high dimensional accuracy. Furthermore, since sufficient sintering is possible even at a low temperature, high bonding strength can be secured.
In particular, since the alloy layer as an upper layer in this invention contains copper and/or manganese besides nickel, a reducing melting point was obtained in baking and the alloy layer formed can hence be a dense layer. Because of this, the ceramic member for bonding can be satisfactorily brazed even without a post-treatment, e.g., nickel plating, conventionally conducted after baking. Namely, a considerable simplification in production process is possible.
Although the alloy layer as an upper layer may have been formed directly on the lower layer formed by metallization, an interlayer differing in constitution from each of the lower layer formed by metallization and the alloy layer as an upper layer may have been formed between the lower and upper layers.
(16) The invention of item 16 is
the ceramic member for bonding of item 15, wherein the metallic layer formed by metallization comprises from 71 to 88% by weight molybdenum and from 0.7 to 5.5% by weight nickel.
In this invention, since the layer formed by metallization contains nickel in an amount of 0.7% by weight or larger, it can have undergone sufficient sintering even at a low temperature. Moreover, since the nickel content therein is 5.5% by weight or lower, the molybdenum has been prevented from excessively sintering and, hence, the strength of bonding between the ceramic base and the layer formed by metallization can be prevented from being insufficient.
Furthermore, since the layer formed by metallization contains molybdenum in an amount of from 71-88% by weight, it is a tenacious layer.
(17) The invention of item 17 is
the ceramic member for bonding of item 15 or 16, wherein the metallic layer formed by metallization further contains from 3.0 to 18.0% by weight silicon oxide ingredient in terms of oxide amount.
In this invention, since the layer formed by metallization contains a silicon oxide (SiO2) ingredient in an amount of from 3.0 to 18.0% by weight, it is exceedingly tenaciously bonded to the ceramic member.
(18) The invention of item 18 is
the ceramic member for bonding of any one of items 15 to 17, wherein the alloy layer comprises from 36 to 61.3% by weight nickel and either from 33 to 60% by weight copper or from 2 to 30% by weight manganese.
In this invention, since the alloy layer contains nickel in an amount of from 36 to 61.3% by weight, the strength of bonding between the alloy layer and the layer formed by metallization is high and high airtightness is obtained.
Furthermore, since the copper content in the alloy layer is 33% by weight or higher, the alloy layer has excellent suitability for brazing and high strength. Moreover, since the copper content therein is 60% by weight or lower, this contributes to an improvement in the strength of bonding between the ceramic base and the layer formed by metallization. On the other hand, since the manganese content in the alloy layer is 2% by weight or higher, the alloy layer has excellent suitability for brazing and high strength. In addition, since the manganese content therein is 30% by weight or lower, this contributes to an improvement in the strength of bonding between the ceramic base and the layer formed by metallization.
(19) The invention of item 19 is
the ceramic member for bonding of any one of items 15 to 18, wherein the interlayer formed between the metallic layer formed by metallization as a lower layer and the alloy layer as an upper layer is an interlayer comprising a nickel-molybdenum alloy.
This invention shows an example of the components of the interlayer. Although the interlayer may generate depending on sintering conditions, etc., the presence of this interlayer exerts little influence on properties including boding strength.
(20) The invention of item 20 is
a bonded object obtained by bonding a metallic member to a ceramic member for bonding of any one of items 15 to 19 through at least the metallic layer formed by metallization and the alloy layer.
In this invention, the ceramic member for bonding and the metallic member have been bonded to each other through the layer formed by metallization and the alloy layer described above. More specifically, the ceramic member for bonding, obtained by forming a metallic layer by metallization on a surface of a ceramic base and further forming an alloy layer on the metallic layer, has been united with the metallic member by bonding the alloy layer to the metallic member with, e.g., a brazing material. The ceramic member may have the interlayer between the layer formed by metallization and the alloy layer.
Consequently, there is no need of conducting nickel plating (of the surface of the layer formed by metallization) and subsequent sintering as in conventional processes, and the metallic member can be directly bonded to the alloy layer by brazing. Therefore, the bonded object can be produced through a smaller number of steps at low cost. Furthermore, this bonded object has high bonding strength and high dimensional accuracy.
(21) The invention of item 21 is
a bonded object obtained by bonding two ceramic members for bonding of any one of items 15 to 19 to each other through at least the metallic layer formed by metallization and the alloy layer of each ceramic member.
In this invention, the two ceramic members for bonding have been bonded to each other through the layers formed by metallization and the alloy layers described above. Each ceramic member may have the interlayer described above between the layer formed by metallization and the alloy layer.
An example of this bonded object is one obtained from two ceramic members for bonding each having a metallic layer formed by a metallization and an alloy layer by bonding the alloy layers to each other with a brazing material.
Consequently, the nickel plating and subsequent sintering conducted in conventional processes are unnecessary as in the case of the bonded object of item 20, and the alloy layer can be directly bonded to a metallic member by brazing. Therefore, this bonded object can be produced at low cost and has high bonding strength and high dimensional accuracy.
(22) The invention of item 22 is
a vacuum switch having the bonded object of item 20 or 21.
The vacuum switch of this invention is characterized by having either of the bonded objects described above. An example of this vacuum switch is an electric circuit switch employing a ceramic insulating valve, in particular one suitable for the switching of high-voltage large-current electricity.
(23) The invention of item 23 is
a vacuum vessel comprising the bonded object of item 20 or 21.
The vacuum vessel of this invention (e.g., an insulating valve) is used in, e.g., the vacuum switch described above. A vacuum switch (electrical circuit switch) can be fabricated by disposing electrodes and other necessary members in this vacuum vessel.